fix(rule): exports as node modules

Author: azu

src/sentence-length.js

@@ -7,7 +7,7 @@ import { RuleHelper } from "textlint-rule-helper";
 const defaultOptions = {
     max: 100
 };
-export default function(context, options = {}) {
+module.exports = function(context, options = {}) {
     const maxLength = options.max || defaultOptions.max;
     const helper = new RuleHelper(context);
     const { Syntax, RuleError, report } = context;

test/sentence-length-test.js

@@ -1,7 +1,7 @@
 // LICENSE : MIT
 "use strict";
-import rule from "../src/sentence-length";
 import TextLintTester from "textlint-tester";
+const rule = require("../src/sentence-length");
 
 const tester = new TextLintTester();
 tester.run("textlint-rule-sentence-length", rule, {